Multi-exchange telephone system.



H. D. CUBRHZR & R. I. UTTER.

MULTI-EXCHANGE TELEPHONE S YSTEM.

APPLICATION FILED DEC.26.,\9I4.

Patented Sept. 4, 1917.

2 SHEETS-SHEET 1.

m mxmmm uvnw NN D H. D. CURRIER 61 R. I. UTTER MULTl-EXCHANGE TELEPHONE SYSTEM.

Pate'ntedSept. 4, 1917.

2 SHEETS-SHEET 2 APPLICATION FILED DEC.26.1914.

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n m nm jhl/EZYZBFEJ 5 5F512? 1717212? z'Er'. Hz Zzazji [U211 I-IIRAM D. CURRIER, OF CHICAGO, AND RICHARD I. UT'IER, OF OAK PARK, ILLINOIS,

ASSIGNORS TO KELLOGG SWI'ICI-IBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLI- NOIS, A CORPORATION OF ILLINOIS.

MULTI-EXCHANGE TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Sept. 4, 1917.

7 '0 all whom it may concern:

Be it known that we, HIRAM D. CURRIER, a citizen of the United States of America, residing in Chicago, and RICHARD I. U'r'rnn, a citizen of the United States of America, residing inOak Park, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multi Exchange Telephone Systems, of which the following is a specification.

Our invention relates to telephone systems, being directed in general to multiexchange telephone systems with means for interconnecting the subscribers stations. of the same and different exchanges, one of the main objects of our invention being to provide a system of theabove character having improved circuit arrangements whereby the special B or trunking operators are eliminated.

In most of the multi-exchange telephone systems of the manual type, that is, wherein operators are provided for manipulating the cord and trunk circuits, the A operators use operators cord circuits for interconnecting the lines of their own exchange but when they desire to connect with a line in a distant exchange they connect to a trunk circuit terminating before a B or special trunking operator in the distant exchange who connects the trunk circuit to the wanted line.

In accordance with our present invention, combination operators cord and trunk circuits are provided whereby an operator may use cord circuits of her position for interconnecting telephone lines terminating thereat or she may receive incoming calls over trunk circuits which may be switched into connection with the calling ends of her cords and in this way use one end of the cord circuit for extending such a. trunk connection to lines terminating in her own exchange. Thus one of the features of our invention is the provision of such combination cord and trunk circuits.

Another feature of our invention is an improved trunk circuit also capable of use as an orderwire so that special orderwires between exchanges are eliminated.

Another feature of our invention lies in an improved means for indicating preferably by visual signals when any operator is busy so that the operators at the distant exchanges, by observing signals corresponding to orderwire keys at their positions, can tell at a glance and without any preliminary testing, those operators who are idle and ready to receive trunked calls.

In working out our invention various new features are introduced and these will be more particularly referred to in the ensuing specification and claims.

For a better understanding of our invention reference is to be had to the accompanying drawings comprising part-s 1 and 2 which, when joined, illustrate diagrammatically the preferred arrangement of our circuits. All parts have been shown at normal with like reference characters indicating parts having like functions. The apparatus shown in part 1 is located in one exchange and the apparatus in part 2 in another, being connected by the heavily marked trunk conductors terminating at the ends of the sheets. Although in illustrating our invention we have shown a plurality of batteries it is to be understood that those shown in part 1 indicate a single exchange battery and those in part 2 a battery in the corresponding exchange.

Referring now more in general to the preferred form of our invention, it comprises exchanges C and D. At the exchange C a plurality of substations as A are provided terminating in line circuits L before a number of different operators positions in multiple jacks each of which has a line signal so that when a call is initiated a plurality of such signals are lighted and thus a number of operators are apprised of the call. For interconnecting the substations a plurality of cord circuit-s13 are provided at each of the operators positions, each cord circuit including answering and calling plugs AP and CP connected by the heavily marked tip and sleeve conductors with the interposed condensers. At the answering end of the cord circuit an answering sleeve relay AS is provided together with an answering tip relay AT. A test relay TE is also provided being of a high resistance, this relay operating when a called line is connected with so as to connect the answering sleeve relay AS to the sleeve strand of the cord and thus to the cut-off relay and calling line circuit.

As above referred to We have embodied our invention in the so-called associated mutiple system, that is a system employing a number of calling line lamps. The first operator to seize the calling line does so to the exclusion of the others for reason of the high resistance test relay TE which operates in the first cord which seizes the line but does not operate in those cords which may be subsequently connected to the calling line. e also employ instantaneous disconnect and recall and to this end a link disconnect relay LD is provided which is energized when the calling subscriber replaces his receiver and thus disconnects the link conductors so that a recall may be initiated without awaiting the removal of the connected plug. At the calling end of the preferred form of cord circuit employed, a calling sleeve relay GS and a calling tip relay OT are provided together with a ringing control relay RC and interrupter relay IR, so that automatic ringing may be employed. A party line ringing key RK is also provided being preferably of the indicating type and having a set of common contacts 21 which areinomentarily actuated each time a ringing plunger is fully depressed but restored when the plunger assumes its indicating position.

' Automatic listening is also provided, this being effected by the connection and disconnection of the operators telephone O by the answering and calling sleeve relays, respectivelv.

An operators telephone O, including the usual transmitter, induction coil and receiver, is common to each operators cord circuits, and also common to each operators Cry telephone are relays AB, BI, and OD.

Before each operator a plurality of trunk jacks J, are positioned, said jacks being connected to trunk circuits T, T extending to exchange D, said jacks being preferably distributed along the board so that all operators have access to these trunks, jacks J and y' appearing before operator No. 1, jack J and j before operator No. 2, jacks J 2 and 7' appearing before operator No. 3, etc. Thus, any of the operators have access to the group of trunks including T and T In communicating between exchanges the operators use the trunks for ordering up connections and the circuit arrangement is such that as long as there is an idle trunk to the distant exchange, there is, of course, an idle orderwire. The circuit arrangement also is such that when an operator presses an orderwire key as OK she connects her telephone in bridge of all of the idle trunks of the group extending to the desired exchange, this being brought about by the connection of her telephone to outgoing orderwire conductors 1, 2 and the operation of all of the operators cut-in relays OO of the selected group, whereby her telephone set is connected through contacts of the relays OO to the idle trunks. As long as a trunk is in use, the combined cut-off and group-busy relay CO is energized so-that although the associated operators relay OC be energized, the relay G0 has rendered it ineffective upon the busy trunk, l i

In exchange O we have shown orderwire keys for three operators positions, these keys being indicated as OK, .OK and OK of operators positions 1, 2 and 3, respectively. These keys are multiply connected to the outgoing orderwire conductors 1, 2, so that any of the operators may connect a telephone set to the trunks T, T Upon actuation of any orderwire key OK all busy lamps BL, BL BL etc, of the seized orderwire are illuminated indicating that the particular associated group of trunks are being used for an orderwire. Of course these lamps are only lighted during the period of ordering between operators.

It will be understood that the operators positions 2 and 3 corresponding to keys 0K and 0K are also provided with an operators telephone 0 and associated apparatus OD, BI and AB, although only keys 0K and OK are shown at the positions 2 and 3.

Should the orderwire key OK be depressed, the operators telephone-disconnect relay OD is energized to disconnect the listening conductors 3, A from her telephone set so that conversation over the orderwire cannot be interfered with or overheard by the calling subscriber. The closing of contact 53 of the key, operates the relays OO of the corresponding group of trunks.

Referring again to trunks T, T these extend preferably to a single operator in exchange D, the trunk T at exchange D being fully illustrated, but only a portion of T both trunks of course being the same. Each trunk T ispreferably individual to a cord circuit B a trunk kev TK being provided for each cord for converting it from an oper- .ators cord circuit into the incoming end of a trunk. Thus, if a connection is to be extended over'the trunk T to the cord B the actuation of. key TK will disconnect the answering end of the cord and connect the trunk T in place thereof, the actuation of key TK also causing the energization of trunk connecting relays TO and TO Thus the high resistance relay H is placed in series with the bridged tip and sleeve relays OS and CT of cord B, causing the actuation iso of H but not permitting the energization of the tip relay CT until the cord calling supervisory signal control relay CS has'been operated when the called subscriber responds.

We preferably arrange the trunks in groups with their outgoing ends, that is the jack J end, multipled before all of the operators in the exchange and with each group terminating at their incoming ends, before a single operator. However, each operator may have several such groups of outgoing trunks to each exchange, each group terminating at its incoming end before a single operator. Each operator has incoming trunks from one exchange only but there may be two or more operators in one exchange each having a group of trunks from the same exchange. For instance the group of trunks including T and T in exchange G terminate at the position of operator #1 in exchange D, the orderwire buttons OK, 0K and OK at exchange C being pro vided at the operators positions of exchange C for this group of trunks.

Assuming a second set of outgoing trunks are provided from exchange C to exchange D, such trunks would bemnltipled before the exchange C operators and connected to a pair of outgoing orderwire conductors 1, 2 niultipled to corresponding order-wire keys at the diflTerent operators positions. Each such key would be multiply connected to the corresponding operators telephone 0 at points 10 and 11, the contacts 53 of this second set of keys being connected to a conductor as 153 extending to the relays QC of this second group of trunks. The contact 13 of each key would be connected to the corresponding operators relay OD as is indicated by the multiple contacts 13 13 The contacts as l i 'of the orderwire keys corresponding to this second set of trunks would be connected to a relay TOB individual to said second set of trunks. Thus it will be seen that no matter which ordcrwire key of her set an operator may actuate, her relay OD is operated to disconnect her telephone from the answering conductors 3, 4 but the relays T013 and ()C of the selected group of trunks only are operated, these last said relays being individual to the selected key and set of trunks. That is, there is a relay TOB for each set of trunks, said relay being connected thereto by commons 7, 8.

' Thus it will be seen that the actuation of an orderwire key will also operate the corresponding relay TUB to light the corresponding busy lamp as BL and thus indicate to the other operators that have access to the corresponding trunks that they are being used for orderwire purposes.

Each operator who is provided with incoming ends of trunks such as T at operator No. 1 exchange G, has a pair of incoming orderwire conductors 5, 6 connected to her telephone and in bridge of all the incoming trunks at her position. It will be remembered that the preferred arrangement is to have each operator provided with incoming trunks from one exchange only. Therefore as long as an operator is busy answering calls one or both of the busy relays AB, BI, are operated so that the incoming conductors 5, 6 of her position are connected together resulting in the operation of the relay as T013 corresponding to her set of incoming trunks so that her busy condition is indicated to the operators at the distant exchange having access to the trunks terminating at her position. In as much as; the incoming orderwire conductors 5, (3, are connected in bridge of all the incoming trunks of the group terminating at her position, it will be seen that an operator is available as long as there is an idle trunk in the group incoming to her position.

lVhenever a set of trunks is in use and is connected to at its jack end, all of the cutoff relays CO of said group of trunks are energized and therefore the conductor 154 which extends serially through the contacts 155 of these relays is connected to ground.

so that the busy lamps BL corresponding to this group of trunks are lighted.

Fromthe foregoing it will be understood that at the outgoing end of each set of trunks, conductors 12, 7-S, 153, and 154: are common and at the incoming end of each set of trunks the incoming orderwire conductors 5, 6, are common.

At exchange D the individual circuit arrangements are the same as those shown at exchange C so that the circuits have corre sponding reference characters-and their likeness will thus be more apparent. The incoming orderwire conductors 5 6 are connected in common to both trunks T and T and it will be understood that the outgoing order-wire conductors 7 8 are to be connect ed to all of the trunks as T -of the corresponding group, although but a single trunk is shown. Likewise conductors 153 and 154 are common to the correspi'mding group of trunks' To the end that an operator seeking a trunk connection may see at a glance what distant operators in the desired exchanges are idle, we have arranged the busy lamps BL in such a way that as long as an operator is inthe act of answering any call, the lamps associated with the out-going ends of the trunks extending to her position will-indicate such a busy condition.

Having described in a general. way the preferred arrangement of our invention, we will now describe in general the method of extending local and trunk connections.

Referring to exchange C, and assuming that two local substations are to be conneetfill) ire ed, a cord circuit B is used by connecting the answering plug AP to the calling line and the calling plug OP to the called line.

As previously referred to, automatic listening is employed, and therefore, when the answering plug AP of the cordcircnit is inserted into the jack of a calling line, the listening conductors 3, 4t, are connected in bridge of the cord circuit, whereby the op erators answering busy relay AB operates to cause the energization of the associated busy indicating relay BI which in turn con neots the incoming orderwire conductors 5, 6, so that the lamps BL, BL, BL in exchange D are lighted. Thus the operators at these positions are apprised of the fact that the operator to whose position orderwire keys OK, OK and OK- have access, is busy.

As soon as said operator No. 1 at exchange C completes such local connection, the listening conductors 3, A, are disconnected and relays AB and BI restore, and efface lamps BL, 1 1; BL in exchange D indicating to.

the operators at these lamp positions that the sa1d operator at exchange O is again idle. Assuming that a trunk connection is to be set up, upon initiation of a call No. 1 operator inserts the answering plug AP operating relays AD and BI, as above, thus indicating her busy condition by the illumination of lamps BL, BL and BL at the distant exchange as before referred to.

Ordinarily an operator has 15 or more cord circuits like B at her position, and the trunks as T associated with the different cords of her position are preferably incoming from one exchange, and as the incoming orderwire conductors 5, 6, are connected to all of these incoming trunks as T the crossing of these conductors 5, 6, by the operation of relay BI lights lamps BL, BL and BL of exchange D. It will thusbe seen that while operator No. 1 is putting up a connection referred to, her busy condition is indicated to all operators having access to her position.

The No. 1 operator having ascertained the calling line desires connection with a line in exchange D,'depresses the orderwire key OK at her position, this act connecting her set 0 to outgoing orderwire 1, 2 and at the same time operating relay OD to disconnect her listening conductors 3, 4: from cord B so that the calling subscriber does not hear her order up the connection. Also responsive to key OK busy indicating relay TOB is actuated to light the lamps BL BL and BL so that the other operators will not attempt to connect with this same group of trunks, while being used by operator No. 1 of exchange O.

Relays DC at all the outgoing trunks T, T etc, of the selected group are also actuated due to the closing of the alternate ground 53 of key OK and outgoing order wires 1, 2, are connected to these trunks T N0. 1 operator of exchange C now converses with operator No. 1 exchange D, over a path including all idle trunks T of the group, to the incoming orderwire conductors 5 6 extending to operator No. 1 exchange D.

The originating operator now calls for the number in the distant exchange, and the distant operator assigns the trunk T, whereupon the originating operator restores the orderwire key OK, and inserts the calling plug OP into the jack J. This energizes cut-off relay CO, and prevents any operator from connecting her outgoing orderwire conductors 1, 2, with trunk T. At the time the distantoperator assigned trunk T, she actuated the trunk key TK of cord B associated with trunk T, thereby operatively connecting the trunk and cord, and disconnecting the answering end of the cord B The actuation of key TK operates relays TC and T6 so that the trunk talking eonductors of T are removed from the common orderwire connection 5 6 At the time operator No. 1 in exchange C depressed her order key OK to communicate with operator No. 1 in exchange D, relay B1 was energized to short circuit con: ductors 5, 6, this in turn short circuiting the talking conductors of trunk T 2 and thus conductors 7 S of exchange D resulting in the operation of trunk operated, busy relay TOB whereby lamps BL, BL and BL are lighted to indicate to the corresponding operators that the group of trunks T, T are in use for orderwire purposes. Therefore the operators in exchange D having access to these trunks will not attempt a connection therewith while the said lamps'are lighted. As this short circuit exists only during the ordering and connecting period of the operators of exchanges C and D, the referred to busy indications exist only during this period.

The operator at exchange D having received the number of the wanted line, inserts the calling plug CP into the ack thereof and then applies the proper ringing current to the line.

The operator at exchange O having restored the key 'OK and inserted the calling plug GP into the jack J of the assigned trunk T caused the restoration of relays OD, BI and AB, whereby the previously referred to busy indications at the distant exchange D and other operators positions of exchange O are removed.

0 pemtion.

In initiatlng a call a subscriber removes the receiver at substation A thereby operating the line relay and lighting the associated line lamps. The first operator to seize the call by the insertion of an answering plug AP, connects the cut-off relay and test relay TE in series effecting the energization of TE but not the cut-off relay due to the comparatively high resistance of relay TE. Therefore relay TE closes its alternate con tact l6 connecting answering sleeve relays AS in circuit with the cut-off relay effecting the energization of both followed by the cnergization of the answering tip relay AT so that the answering supervisory lamp AL does not light.

By the operation of AS and the closing of its alternate contacts 17, 18, listening conductors 3, 4-, are connected through normal contacts 19, 20, in bridge of the talking conductors of the cord so that the operators telephone 0 is automatically connected to the calling line.

Should a second operator insert an answering plug AP subsequent to the insertion of the first plug, the test relay TE of this second cord circuit will not operate due to the shunting effect of the relay AS of the first cord so that the second operator is unable to communicate with the calling subscriber and knows that the call has bee seized by another operator.

vVhen plug AP is inserted and relay AS energized, answering busy relay AB is oper'ated over a circuit including conductor 3, .alternate contact 18, normal contacts 20, 32,

and relay CS to battery. However, relay CS does not energize due to the high resist ance of relay AB. Responsive to operation of AB, relay BI is operated to close its alternate contacts 43, 441, and thus cross the incoming orderwire conductors 6, 5, so that the trunk conductors 45 and 46 are crossed, and tracing this circuit through normal con tacts 4:7 48 at relay C0 of T normal contact 49 50 and conductors 7 to ground and battery through relay TOB, it will be seen that the last said relay is operated to light lamps BL, BL and BL. Thus the operators at exchange D that have access to operator No. 1 of exchange C are apprised of her busy condition. Therefore should they desire to extend a trunking connection to exchange C they will communicate over some other set of trunks than that set including trunk T The operator now ascertains the number of the wanted line and inserts the calling plug CP into a jack thereof, (which line is similar to that of A) thereby connecting the cut-off relay of this line and the calling sleeve relay CS in series and effecting the energization of both. It will be noted that normal contacts 19, 20 are interrupted When relay CS energizes, thereby automatically disconnecting the operators telephone from thecord. This effects the restoration of relays AB, BI, aIldTOB so that lamps BL, BL, BL are cifaced.

lVhen plug CP is inserted, lamp CL is lighted but is again effaced when the ringing key is actuated, due to the interruption of normal contact 25 of relay RC.

The operator now actuates the proper plunger of the ringing key RK to connect a ringing generator G of the proper frequency to the called line, the full actuation of the plunger causing a momentary actuation of the common contact 21 whereby the ringing control relay RC is energized over a path traced from battery through the winding of the relay, alternate contact 21, conductor 23 to ground at alternate contact 24. Relay RC therefore operates and locks itself through its alternatecontact 25 to the previously mentioned ground. Upon the return of the ringing plunger to its indicating position the generator contact remains closed but contact 21 returns to its normal position establishing an operating circuit for the interrupter re lay IR traced from battery through the interrupter I, the winding of IR, alternate contact 26, normal contact 21, conductor 23, to ground at alternate contact 24. Relay IR therefore periodicallyv energized to operate its contacts 27, 28 whereby ringing current and calling tip relay CT are alternately connected in bridge of the called line.

Upon response of the called subscriber a circuit for relay CT is established from ground through the Winding thereof, normal contact 27 alternate contact 29, through the plug CP and over the called line returning through relay CS to battery. Relay CT therefore energizes interrupting its normal contact 30 to effect the restoration of relay RC whose contact 26 is interrupted to prevent further actuations of the interrupter relay Ed. The closing of normal contacts 32, 33 of RC establishes the continuity of the talking conductors of the cord and thus the two substations are connected in a conversational circuit.

hen the subscribers have finished conversation they replace their receivers in the ordinary manner to effect the restoration of the tip relays AT and CT, the restoration of CT causing the illumination of calling supervisory lamp CL over a circuit traced from battery through said lamp, normal contacts. 64., 25, 30 to ground at alternate contact 24.

At the answering end of the cord the restoration of relay AT establishes an energizing circuit for the link disconnect relay LD and a circuit for lamp AL by the closing of normal contact 36 which is grounded through alternate contact 37 andconductor 23 to ground at alternate contact 24. Relay LU therefore interrupts its normal contacts 38,

39 to op'eratively disconnect the link conductors from the line of substation A so that the .line is available for a recall without awaiting the disconnection of the plug AP from the jack. The closure of alternate contact 40 of relay LD maintains the relay AS energized from the ground previously traced to contact 36 of AT. I

The operator observing the two signals AL and CL removes the plugs from their respective jacks, the removal of plug GP elfecting the restoration of CS whereby its alternate contact 2A is interrupted to remove ground' from the locking circuit of relays AS, LD and TE effecting their restoration, so that the cord circuit apparatus is again at normal.

' Trunk connection.

lVe will now describe the operation of the system in establishing a connection between substations A and A of exchanges G and D respectively.

To initiate a call a subscriber at substation A removes his receiver to light his line lamps whereby the first cord circuit connected therewith seiZes the call as before described. This connection results in the energization of relays AS, AT and the-cutoff relay of the calling line so that by relay AS the operators telephone 0 is connected over the listening conductors 3, A to the cord circuit and thus to the calling substa tion.

The operator, finding that connection is desired with a substation in exchange D, and noting that the group of trunks corresponding to key OK is available for order purposes, depresses key OK at her position which key extends to the group of trunks including T, T going to operator N0. 1 of exchange D.

At the time the operators telephone 0 was connected in bridge of the cord circuit B by the actuation of relay AS, a circuit for the answering busy relay AB was established whereby busy lamps BL, BL, BL corresponding to all orderwire keys OK, 0K, 0K connected to the particular group of trunks from exchange D extending to operator No. 1 of exchange C, are lighted. Andas we preferably have all the incoming trunks at an operators position coming from one exchange it will be seen that by illuminating lamps BL, BL, BL, the busy condition of OPR No. 1,'exchange C, is indicated. to the operators of exchange D and they may then communicate with another operator in exchange C over another set of trunks.

This energizing circuit for relay AB, which relay by the way is of a comparatively high resistance, is traced from ground through the winding thereof, listening conductor 3, alternate contact 18, normal con tacts 20, 32, the winding of CS to battery causing the energization of AB but not CS. Alternate contact 42 of relay AB is therefore closed causing the energization of busy indicating relay BI which relay closes its alternate contacts 13, A4, short circuiting incoming orderwire conductors 5, 6, thereby also short circuiting or connecting together the tip and sleeve talking conductors 15, 46 of the group of trunks T coming to this operators position from exchange D. Tracing these conductors 45, A6 of trunk T to exchange D, they follow a path through normal contacts 47 18 and normal contacts 49 50 conductors 8 7 and relay T013 to battery and ground resulting in the energization thereof. Belay TUB- therefore closes its alternate contact 151 and lights lamps BL, BL, and BL of the operators order wire keys in exchange D which control the group of outgoing trunks including T extending to operator No. 1 at exchange C. These operators at exchange D are thus apprised of the busy condition of operator N0. 1 at exchange C. As already referred to, these operators at exchange D may be provided with a second set of outgoing trunks to exchange C, which trunks would extend to some other operator than No. 1 at exchange C so that they would not be delayed should one set be busy.

Referring again to operator No. 1 at ex.- change G, having depressed the proper orderwire key OK as already referred to, its contacts 13, 11 are closed connecting relays TOB and OD in series causing the energization of both, the closing of alternate contact 151 of TOB lighting lamps BL, BL and BL so that operators No. 2 and No. 3 who also have access to the outgoing orderwires 12 will not attempt to communicate thereover while these lamps are lighted. By the interruption of normal contacts 51, 52, the operators telephone 0 is disconnected from her cord circuit. The closing of alternate contact of OK causes the ei'iergization of the operator connecting relays 0G in the selected group of trunks T, T extending the operator No. 1 at exchange D and therefore these relays OC connect the outgoing orderwire conductors 1, 2, through the alternate contacts a9, 50 of each relay and the corresponding normal contacts 47, A8 to the talking conductors 58, 59 of all the idle'trunks in the group, the circuit then continuing to the distant exchange and through'the normal' contacts 60 (51 of the relays TC of these idle trunks and over the incoming orderwire conductors 5 6 through normalcontacts 43 4: 1 and 51 52 to the operators telephone It will also be noted that whena key UK is thrown, the upper winding of relay B1 is energizedbut as the lower winding is energized by AB while putting up a'connection,

this upper circuit through BI is not necessary. This upper circuit is useful only when an operator desires to communicate with a distant operator without having a plug AP up. At such time relay BI would energize and indicate the busy condition of the operator.

Operator No. l at exchange C now calls for the wanted substation from operator N0. 1 at exchange D and we will assume the exchange D operator assigns trunk T which corresponds to her cord circuit B After testing the wanted line in the usual way and also throwing the trunk converting key TK the exchange D operator inserts the calling plug CP in the jack of the called line and presses the proper plunger of her ringing key BK This of course momentarily actuates the common contact 21 so that ringing control relay RC and interrupter relay 1R are actuated in a manner as already described so that ringing current is applied to the called line.

The exchange G operator upon having trunk T assigned for connection restores key OK and then inserts calling plug GP into the jack J thereof, thereby connecting relays CS and CO in series and causing the energization of both. The operation of relay GS disconnects the listening conductors 3, a from this particular cord and the operation of CO interrupts normal contacts 6L7, 48 thereof and thus prevents interference with conversation over trunk T.

The restoration of key OK by operator No. 1, of exchange C disconnects telephone 0 from the outgoing orderwire conductors 1, 2 and also restores relays TOB and OD. Restoration of TOB extinguishes lamps BL, BL and BL so that the other operators in exchange C which have access to orderwire 1, 2, and the group of outgoing trunks T, T know that this group is available for orderwire and out-trunking purposes.

The restoration of relay OD eifects the restoration of the relays 0C corresponding thereto, that is the relays DC of the particular group of trunks T, T extending to operator No. 1 in exchange D.

The insertion of plug GP and consequent energization of CS causes restoration of relays AB and B1 to interrupt the short circuit across incoming orderwire conductors 5, 6, so that relay TOB at exchange D is restored extinguishing lamps BL, BL and BL whereby the operators thereat are apprised of the fact that the outgoing trunks from their exchange to operator No. 1 at exchange 0 are available for further orderwire purposes and opt-trunking Referring again to circuit B at exchange D it will be remembered that the converting key TK was thrown whereby the closure of itsalternate contacts 62 63 connected the talking conductors of the cord with trunk circuit T, at the same time disconnecting the answering end of the cord B The closure of alternate contact 6& of the key effects the energization of relays TC and TC the operation of TC disconnecting the incoming orderwires 5 6 and connecting the talking conductors 58, 59 through to the repeating coil. The operation of relay TC connects the cord callingsupervi- .sory-signal control relay SC in circuit to be controlled by the relay GT when the called subscriber responds. Also due to the closing of alternate contacts 74 of relay T0 vthe calling lamp GL acts as a guide lamp and is illuminated if the operator at exchange C plugs into the assigned trunk prior to the connection of the trunk to the called line, or if the wrong trunk is plugged into by the originating operator, this act would be indicated by the corresponding lamp remaining lighted;

lVhen the originating operator inserts the calling plug GP into the trunk jack, relay H of the trunk is connected in series with relays CT and CS, said relay H energizing but due to its comparatively high resistance preventing the energization of relay CT. Thus relay CS being energized and relay CT at normal, the calling lamp CL of cord B is lighted and remains so until the called subscriber responds.

We have previously referred to the conuection of cord B to the wanted line and the application of ringing current thereto. Upon a response being received from the called substation tip relay GT is energized resulting in the interruption of its normal contact 27 to prevent further application of ringing current. The closure of alternate contact 27 connects signal control relay SC in circuit with ground at alternate contact 24 of CS resulting in the operation of SC and thus shunting relay H whereby its alternate contact 67 is interrupted to efi'ace lamp GL of cord B The connection of the shunt around the winding of relay H results in the energization of relay CT at cord B whereby its normal contact 30 is interrupted etlacing the calling lamp CL so that the originating operator knows that the called subscriber has responded.

Substations A and A are now connected over the conversational circuit indicated by the heavily marked conductors of the circuits referred to.

When disconnection is desired the receiw ers at substations A and A are replaced, the replacing at substation A resulting in the deenergization of the tip relay AT and the energization of relay LD and the lighting of lamp AL as already described. The replacing of the receiver at A effects the restoration of the tip relay GT resulting in the lighting of supervisory lamp GL over a circuit traced from battery through the lamp, alternate contact 7& normal contacts 67 69 and alternate contact 24: to ground.

Also responsive to the restoration of relay GT at exchange D, and due to the interruption of its alternate contact 27 relay SC restores removing the shunt from around the winding of the high resistance relay H and thus effecting the restoration of the tip relay CT at cord B, which re lay restores again lighting lamp CL over the previously traced path. The operators therefore withdraw the inserted plugs from the corresponding jacks, the operator atB also restoring the key TK so that all apparatus is again available for further connections.

e will now assume that the previously described trunk connection has been established and a second trunking connection from exchange C to exchange D is to be established by .opeator No. 2 of exchage C. Operator No. 2 therefore after having answered a call by inserting an answering plug in the calling line jack would know that the group of trunks including T, T is. available and therefore would actuate the corresponding orderwire key 0K Thus she would connect her telephone to outgoing orderwire conductors 1, 2 and also actuate her relay OD and the relay TOB shown, which last relay is of course individual to the said group of trunks. The actuation of relay TOB lights lamps BL, BI), BL to indicate the busy condition of this group of trunks and the actuation of her relay OD disconnects her telephone from the cord circuit used by her. The actuation of OK also operates the orderwire connecting relays DC of this group of trunks but due to the fact that the cut-off relay of trunk T is energized, the orderwire conductors 1, 2 are not connected to this trunk but are connected to trunk T by relay O0 and of. course to any other idle trunk of the group. Relays AB and BI of operator No. 2 of course also actuated at the time of answering so that the conductors 5, 6, leading to the group of trunks incoming to her position are crossed and thus actuate the busy lamps at the distant exchange corresponding to these last said trunks. This, of course, will be understood from the previous description.

The connecting of No. 2 operators telephone across conductors 1, 2 will extend her telephone connection over conductors 58 59 and incoming orderwire conductors 5 6 to operator No. 1 at exchange D so that the connection can be ordered up in a manner as will be understood from the previous description.

As previously referred to when all of the trunks of a group are connected with at their jacks, the corresponding cut-off relays C0, C0 etc., are energized so that the lamps BL, BL, and BL corresponding to this group are lighted. However, as soon as one trunk of the group becomes idle and the plug is withdrawn from its ack the corresponding cut-off relay restores and thus interrupts the conductor 154 and eflfaces the lamps.

In the previously described trunk connections'we have referred to trunk connections outgoing from exchange 0. To extend connections from exchange D to exchange C the operation would be the same and it is be lieved that in view of the previous description further reference to trunking from exchange D to exchange C is unnecessary.

It will be noted that an operators telephone is normally in circuit relation with the incoming trunks at her position so that it is only necessary that the operator at the outgoing end of the trunks connect her telephone therewith and she may immediately converse with the operator at the incoming end of the trunk. However, when an operators telephone is connected to one of her cord circuits in the act of answering 'a call, her telephone is automatically disconnected from the incoming orderwire conductors by the actuation of her busy indicating relay BI.

In illustrating our invention we have connected each outgoing trunk to an operators cord circuit capable of being used for interconnecting local lines, but we also contemplate connecting the trunk circuits at their incoming ends to plug ended circuits adapted for use only in extending trunk connections.

In illustrating and describing our invention we have referred to particular arrange ments, but it will be apparent that after becoming familiar with our invention one skilled in the art will readily see where changes and modifications may be made and therefore we do not desire to be limited to the system as shown and described but aim to cover all that which comes within the spirit and scope of the appended claims.

Having described our invention, what we claim as new and desire to secure by United States Letters Patent, is:

1. A telephone system including two telephone exchanges each having telephone lines terminating at operators positions thereat and cord circuits for interconnecting the lines, groups of outgoing trunk circuits at each exchange having outgoing terminals distributed before the operators positions thereat, each group terminating at its incoming end at a single operators position, an operators telephone at each operators position, an outgoing orderwire for each set of outgoing trunks connected to orderwire keys distributed among the operators positions having access to the corresponding group of trunks, a busy signal for each key and an incoming orderwire for connecting the incoming ends of each group of trunks to the corresponding operators telephone.

2. A telephone system including two telephone exchanges each having telephone lines terminating at operators positions thereat and cord circuits for interconnecting the lines, groups of outgoing trunk circuits at each exchange having outgoing terminals distributed before the operators positions thereat, each group terminating at its in coming end at a single operators position, an operators telephone at each operators position, an outgoing orderwire for each set of outgoing trunks connected to orderwire keys distributed among the operators positions having access to the corresponding group of trunks, a busy signal for each key, an incoming orderwire for connecting the incoming ends of each group of trunks to the corresponding operators telephone, and means whereby when an operator actuates an orderwire key to connect her telephone with an outgoing orderwire a busy signal is operated at each other orderwire key corresponding to the used orderwire.

3; A telephone system including two telephone exchanges each having telephone lines terminating at operators positions thereat and cord circuits for interconnecting the lines, groups of outgoing trunk circuits at each exchange having outgoing terminals distributed before the operators positions thereat, each group terminating at its incoming end at a single operators position, an operators telephone at each operators position, an outgoing orderwire for each set of outgoing trunks connected to orderwire keys distributed among the operators positions having access to the corresponding group of trunks, a busy signal for each key, an incoming orderwire for connecting the incoming ends of each group of trunks to the corresponding operators telephone, and means whereby when an operator has her telephone connected. with one of her cord circuits in answering a call, the busy signals corresponding to the keys at the outgoing ends of the group of trunks extending to her position are operated.

4. A telephone system including two tele phone exchanges each having telephone lines terminating at operators positions thereat and cord circuits for interconnecting the lines, groups of outgoing trunk circuits at each exchange having outgoing terminals distributed before the operators positions thereat, each group terminating at its incoming end at a single operators position, an operators telephone at each operators osition, an outgoing orderwire for each set of outgoing trunks connected to orderwire operated at each other orderwire key cor-v responding to the used orderwire, and means whereby when an operator has her telephone connected with one of her cordcircuits in answering a call, the busy signals corresponding to the keys at the outgoing ends of the group of trunks extending to her posi-. tion are operated.

5. A telephone system including telephone exchanges, telephone lines terminating at operators positions in each of said exchanges with cord circuits for interconnecting said lines, a group of outgoing trunk circuits at one ofsaid exchanges havin outgoing terminals accessible from ,di erent operators positions thereat, an operators telephone ateach position of said exchange, an order wire keyat each position of said exchange common to the cord circuits thereat and connections controlled thereby for connecting the corresponding operators telephone with said trunks, and an operators telephone at the distant exchange normally in circuit relation with said trunks whereby the operators in the first exchange may communicate with the distant exchange operator over said trunks.

6. A telephone system including telephone exchanges, a plurality of operators positions at one of said exchanges having telephone lines and cord circuits for interconnecting said lines, telephone lines terminating at an operators position in the distant exchange, trunk circuits having .outgoing ends at the first exchange connected multiply to jacks at the different operators-positions thereat and extending to incoming ends at the distant exchange adapted for connection with the telephone lines thereat, operators telephones at the first said ex change positions, an operators telephone at the distant exchange in circuit relation with said trunks, and means whereby any of the said operators telephones in the first exchange may be connected with-said trunks for communication with the distant operator independent of connection with the trunks at their outgoing ends by the associated cord circuits.

7. A telephone system comprising telephone exchanges, telephone lines, cord circuits at each of the exchanges, jack ended out going trunk circuits at each of the exchanges, operators telephones, and electro magnetically controlled means whereby an operator may connect her telephoneto a trunk circuit extending to the desired distant' exchange and communicate thereover as an orderwire prior to the connection oi? the cord circuit with such trunk.

8. A telephone system including telephone exchanges, trunk circuits connecting said exchanges and having incoming and outgoing ends, telephone lines and cord circuits for interconnecting said lines at each of the exchanges, operators telephones at said exchanges for connection with the cord circuits, means for automatically c0nnecting and disconnecting said operators telephones and said cord circuits, and means for connecting said operators telephones and trunks independent of connections between the trunks and cords whereby the operators may communicate with each other over said trunk circuits.

9. A telephone system including telephone lines and cord circuits for interconnecting the same, an operators telephone for connection with the cord circuits, incoming trunk circuits at the exchange, means nor mallyconnecting said operators telephone to the trunk circuits, and automatic means for disconnecting the operators telephone from the trunks when connected to the cord circuits.

101A telephone system including telephone lines and cord circuits for interconnectin'g the same, an operators telephone for "connection with the cord circuits, incoming trunk circuits at the exchange, outgoing trunk circuits at the exchange, means for connecting said cord circuits and trunks, and electromagnetic means for connecting and disconnecting the operators telephone and trunks independent of connections between the trunks and cords whereby the said trunks may be used as orderwires.

11. A telephone system including tele-' phone exchanges, telephone lines and cord circuits for interconnecting the lines at one of said exchanges, outgoing trunk circuits extending from said exchange to incoming ends at the distant exchange, telephone lines at said distant exchange adapted to be con nected with by the incoming ends of said trunks, an operators telephone at said distant exchange, means whereby an operator at the first said exchange may communicate with the d1stant operator over said trunks for'order wire purposes prior to the connection of a cord circuit with the outgoingend -'of the trunks, and electromagnetic means for disconnecting the distant operators telephone from said trunk circuits.

12. A telephone system including telephone lines and cord circuits for interconnecting the same, an operators telephone for the cord circuits, outgoing trunk circuits for connection with the cord circuits'in extending outgoing trunk connections, an order-- wire key, and electromagnetic means con trolled thereby for operatively connecting the operato1"s-telepl1one to a plurality of said trunk circuits at one time.

13. A telephone system including telephone lines and cord circuits for interconnecting the same, an operators telephone for the cord circuits, means for automatically connecting and disconnecting said operators telephone and said cord circuits, a group of outgoing trunk circuits for connection with said cord circuits in extending outgoing trunk connections, an 1 orderwire key, and circuit connections controlled by said key for operatively connecting the operators telephone and the idle ones of said trunk circuits. 1 i

14. A telephone system including telephone lines terminating at operators posi tions at the exchange, cord circuits at each of said positions for interconnecting said lines, an operators telephone for the cord circuits of each position, outgoing trunk circuits having multiply connected terminals accessible from the dillerent operators" posi tions for connection with the cord circuits in extending outgoing trunk connections, order-wire keys, and connections controlled by one of said keys for connecting one of said operators telephones to said trunk circuits and for indicating busy to the other operators during such connection.

'15. A telephone system including telephone lines terminating at operators posi tions at the exchange, cord circuits at each of said positions for interconnecting said lines, an operators telephone for the cord circuits of each position, outgoing trunk circuits having multiply connected terminals accessible from the different operators positions for connection with the cord circuits in extending outgoing trunk connections, orderwire keys and connections controlled thereby for connecting any of the operators telephones and trunk circuits, and signals corresponding to said keys whereby when any key is actuated to connect an operators telephone'to a trunk the signals for the keys corresponding to the trunk of the actuated key are operated to indicate the busy condition of the trunk.

16. A telephone system comprising telephone exchanges, telephone lines terminating at said exchanges, cord circuits at each of said exchanges, operators telephones associated with said cord circuits, means for automatically connecting and disconnecting said operators telephones and said cord cir-- cuits, trunk circuits at each of said exchanges, means whereby an operator may connect her telephone-to one of said trunk circuits and communicate thereover as an orderwire prior to connection of one of said cord circuits with such trunks, and means responsive to the connection of the operators telephone with the trunk circuit for renoering ineffective the means for connecting and disconnecting said operators telephone and cord circuits.

17. A telephone system including telephone exchanges, telephone lines terminating at said exchanges, cord circuits for interconnecting the said lines, trunk circuits extending between said exchanges, means for rendering certain of the trunk circuits that extend between two of said exchanges busy, and means whereby an operator may connect her telephone to the remaining idle ones of said trunk circuits and use said idle circuits as an orderwire in transmitting a message to a distant operator.

18. A telephone system comprising telephone exchanges, telephone lines and cord circuits at each of said exchanges, operators telephones associated with said cord circuits, a group of trunk circuits extending between two of said exchanges, means for extending conversational circuits over part of said group of trunk circuits, and means whereby an operator may connect her telephone to the remaining trunk circuits of the group and communicate thereover as an orderwire.

19. A telephone system including tele phone lines and cord circuits for interconnecting the same, an operators telephone associated with said cord circuits, means for automatically connecting and disconnecting said operators telephone and cord circuits, incoming trunk circuits at the exchange, connections normally extending between said operators telephone and said trunk circuits, means for disconnecting the operators telephone from said trunk circuits when connected to one of said cord circuits, and means for rendering inefi'ective said first means when said operators telephone is operatively connected with an operators telephone at a distant exchange.

20. A telephone system including telephone lines, cord circuits for interconnecting said lines, an operators telephone for said cord circuits, outgoing trunk circuits for connecting with the cord circuits in extending outgoing trunk connections, an order wire key and circuit connections controlled thereby for operatively connecting the operators telephone with the idle ones of said trunk circuits, and means for there after connecting one of said cord circuits with an assigned one of said idle trunks.

21. A telephone system including tele phone lines, operators link circuits for intel-connecting said lines, an operators telephone associated with said link circuits, means t'or automatically connecting an d disconnecting said operators telephone and of said positions for interconnecting said,

lines, an operators telephone associated with each group of cord circuits, outgoing trunk circuits provided with multiply connected terminals accessible from the different operators positions, order-wire keys and connections controlled thereby for connecting any of the operators telephones and said trunk circuits, and means for indicating at-each operators position that one of said order wire keys is in its operated position.

23. A telephone system including telephone exchanges, telephone lines terminating at said exchanges, cord circuits for interconnecting said lines, an operators telephone, trunk circuits extending between said exchanges, means for rendering certain of the trunk circuits that extend between two of said exchanges busy, an order wire key, an electromagnet for each of said trunk lines, and means controlled by said order wire key for energizing the electromagnets associated with the remaining idle ones of said trunk circuits to connect said operators telephone to the said idle trunk circuits.

24. A telephone system including trunk lines extending from one telephone exchange to another, an operators telephone at said first exchange associated with said trunk lines, an operators telephone at said second exchange associated with said trunk lines, means for making certain of said trunk lines test busy, an order wire key, and an electromagnet for each of said trunk lines controllable by said order wire key for connecting the operators telephone at said first exchange over the remaining idle trunk circuits to the operators telephone at said second exchange.

25. A telephone system including a plurality of trunk lines extending from one telephone exchange to another, an operators telephone associated with said trunk lines, a relay for each trunk line for connecting said operators telephone with its associated trunk line, an order wire key, means for making certain of said trunk lines busy, and circuits controlled by said order wire key for energizing the relays associated with idle trunk circuits to connect the operators telephone with said idle trunk circuits.

Signed by us at Chicago, county of Cook, 15 and State of Illinois, in the presence of two 26. A telephone system including a group of trunk llnes extending iroin one telephone exohzrnge to enother, an operators telephone Witnesses.

ussoeiated with sa d trunl lines, an electro- HIRAM D CURRIER magnet for each of said trunk lines fol con- RICHARD I UTTER neeting said operators telephone thereto, and an order Wire key for simultaneously Vitnesses:

energizing said electroinagnets to connect GEORGE E. MUELLER, sand operators telephone to S2L1Cl trunk lines.

M. R. RooHFoRD.

Copies 01. this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. G." 

